I'll look into memmap as Stefan suggested. If Robert Kern's out there,
do you have any comments about what I might be doing wrong.
Id on't know memmap at all yet - basically each file will have multiple
numpy arrays written, read, appended and updated as required.
Brennan
Brennan Williams wrote:
> I've tried replacing numpyio with both fopen and now also npfile but I'm
> getting the same problem, i.e. if I write a numpy array to the file,
> everything else before that position in the file is now zero. It is as
> if it is a new file, not an existing one.
>> Brennan Williams wrote:
>>> I have an existing binary file containing numpy array data. It has been
>> created using open,fwrite & close and I can read the data using fread.
>>>> I want to be able to either append a new array to the end of the file or
>> update an existing array within the file.
>>>> I've tried opening the file with a mode of either 'ab+' or 'wb+' and
>> then writing the data using something like....
>>>> fd = open(vfname, 'ab+')
>> if fd:
>> filepos=(self.id-1)*self.yarray.size*4
>> fd.seek(filepos)
>> fwrite(fd, self.yarray.size, self.yarray,'f')
>> fd.close()
>>>> When I use a mode of 'ab+' it looks like the data has been written to
>> the file ok (no errors reported) but when I read it back I get my
>> original data.
>>>> When I use 'wb+' then my updated data gets written and read back ok. But
>> when I reload the file, everything apart from my updated data (i.e.
>> everything before it in the file) is now zero.
>>>> The '+' in the mode seems to make no difference.
>>>> What am I doing wrong?
>>>> Thanks
>>>> Bren.
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